Pseudohyperaldosteronism: pathogenetic mechanisms

Torsade de Pointes Caused by a Compound Licorice Tablet

The clinical manifestations of licorice-induced pseudoaldosteronism include muscle weakness, periodic paralysis, hypokalemia, and hypertension. Excessive licorice consumption can lead to adverse reactions affecting multiple systems, including the endocrine, cardiovascular, nervous, digestive, and immune systems. Although licorice is a frequently used Chinese herbal medicine, life-threatening adverse reactions have been reported among its users. This article presents a case of severe hypokalemia, torsade de pointes, severe hypertension, and exacerbation of manic symptoms resulting from an overdose of compound licorice tablets. This study aimed to enhance the understanding of the causes of hypokalemia and raise awareness on the potentially fatal adverse reactions associated with licorice drugs.

Pseudohyperaldosteronism Due to Licorice: A Practice-Based Learning from a Case Series

Pseudohyperaldosteronism (PHA) is characterized by hypertension, hypokalemia, and a decrease in plasma renin and aldosterone levels. It can be caused by several causes, but the most frequent is due to excess intake of licorice. The effect is mediated by the active metabolite of licorice, glycyrrhetinic acid (GA), which acts by blocking the 11-hydroxysteroid dehydrogenase type 2 and binding to the mineralocorticoid receptor (MR) as an agonist. The management of licorice-induced PHA depends on several individual factors, such as age, gender, comorbidities, duration and amount of licorice intake, and metabolism. The clinical picture usually reverts upon licorice withdrawal, but sometimes mineralocorticoid-like effects can be critical and persist for several weeks, requiring treatment with MR blockers and potassium supplements. Through this case series of licorice-induced PHA, we aim to increase awareness about exogenous PHA, and the possible risk associated with excess intake of licorice. An accurate history is mandatory in patients with hypertension and hypokalemia to avoid unnecessary testing. GA is a component of several products, such as candies, breath fresheners, beverages, tobacco, cosmetics, and laxatives. In recent years, the mechanisms of action of licorice and its active compounds have been better elucidated, suggesting its benefits in several clinical settings. Nevertheless, licorice should still be consumed with caution, considering that licorice-induced PHA is still an underestimated condition, and its intake should be avoided in patients with increased risk of licorice toxicity due to concomitant comorbidities or interfering drugs.

Apparent mineralocorticoid excess in Israel: a case series and literature review

BACKGROUND AND OBJECTIVE

Apparent mineralocorticoid excess (AME) syndrome is an ultra-rare autosomal-recessive tubulopathy, caused by mutations in HSD11B2, leading to excessive activation of the kidney mineralocorticoid receptor, and characterized by early-onset low-renin hypertension, hypokalemia, and risk of chronic kidney disease (CKD). To date, most reports included few patients, and none described patients from Israel. We aimed to describe AME patients from Israel and to review the relevant literature.

DESIGN

Retrospective cohort study.

METHODS

Clinical, laboratory, and molecular data from patients' records were collected.

RESULTS

Five patients presented at early childhood with normal estimated glomerular filtration rate (eGFR), while 2 patients presented during late childhood with CKD. Molecular analysis revealed 2 novel homozygous mutations in HSD11B2. All patients presented with severe hypertension and hypokalemia. While all patients developed nephrocalcinosis, only 1 showed hypercalciuria. All individuals were managed with potassium supplements, mineralocorticoid receptor antagonists, and various antihypertensive medications. One patient survived cardiac arrest secondary to severe hyperkalemia. At last follow-up, those 5 patients who presented early exhibited normal eGFR and near-normal blood pressure, but 2 have hypertension complications. The 2 patients who presented with CKD progressed to end-stage kidney disease (ESKD) necessitating dialysis and kidney transplantation.

CONCLUSIONS

In this 11-year follow-up report of 2 Israeli families with AME, patients who presented early maintained long-term normal kidney function, while those who presented late progressed to ESKD. Nevertheless, despite early diagnosis and management, AME is commonly associated with serious complications of the disease or its treatment.

Unequal crossing over between CYP11B2 and CYP11B1 causes 11 β -hydroxylase deficiency in a consanguineous family

Cytochrome P450 (CYP) family CYP11B2/CYP11B1 chimeric genes have been shown to arise from unequal crossing over of the genes encoding aldosterone synthase (CYP11B2) and 11β-hydroxylase (CYP11B1) during meiosis. The activity deficiency or impaired activity of aldosterone synthase and 11β-hydroxylase resulting from these chimeric genes are important reasons for 11β-hydroxylase deficiency (11β-OHD). Here，two patients with pseudoprecocious puberty and hypokalemia hypertension and three carriers in a consanguineous marriage family were studied. A single CYP11B2/CYP11B1 chimera consisting of the promoter and exons 1 through 5 of CYP11B2, exons 8 and 9 of CYP11B1, and a breakpoint consisting of part of exon 6 of CYP11B2 and part of exon 6, intron 6, and exon 7 of CYP11B1 were detected in the patients and carriers. At the breakpoint of the chimera, a c 0.1086 G > C ( p.Leu.362 =) synonymous mutation in exon 6 of CYP11B2, a c 0.1157 C＞G(p. A386V) missense mutation in exon 7 of CYP11B1, and an intronic mutation in intron 6 were detected. The allele model of the CYP11B2/CYP11B1 chimera demonstrated homozygosity and heterozygosity in the patients and the carriers, respectively. Molecular docking and enzymatic activity analyses indicated that the CYP11B2/CYP11B1 chimeric protein interacted with the catalytic substrate of aldosterone synthase and had similar enzymatic activity to aldosterone synthase. Our study indicated that deletion of CYP11B1 and CYP11B2 abolished the enzymatic activity of 11 β-hydroxylase and aldosterone synthase; however, the compensation of the enzymatic activity of aldosterone synthase by the CYP11B2/CYP11B1 chimeric protein maintained normal aldosterone levels in vitro. All of the above findings explained the 11β-OHD phenotypes of the proband and patients in the family.

A Novel Approach to Reducing Lung Metastasis in Osteosarcoma: Increasing Cell Stiffness with Carbenoxolone

AIM

Primary malignant bone tumor osteosarcoma can metastasize to the lung. Diminishing lung metastasis would positively affect the prognosis of patients. Our previous studies demonstrated that highly metastatic osteosarcoma cell lines are significantly softer than low-metastasis cell lines. We therefore hypothesized that increasing cell stiffness would suppress metastasis by reducing cell motility. In this study, we tested whether carbenoxolone (CBX) increases the stiffness of LM8 osteosarcoma cells and prevents lung metastasis in vivo.

METHODS

We evaluated the actin cytoskeletal structure and polymerization of CBX-treated LM8 cells using actin staining. Cell stiffness was measured using atomic force microscopy. Metastasis-related cell functions were analyzed using cell proliferation, wound healing, invasion, and cell adhesion assays. Furthermore, lung metastasis was examined in LM8-bearing mice administered with CBX.

RESULTS

Treatment with CBX significantly increased actin staining intensity and stiffness of LM8 cells compared with vehicle-treated LM8 cells (p < 0.01). In Young's modulus images, compared with the control group, rigid fibrillate structures were observed in the CBX treatment group. CBX suppressed cell migration, invasion, and adhesion but not cell proliferation. The number of LM8 lung metastases were significantly reduced in the CBX administration group compared with the control group (p < 0.01).

CONCLUSION

In this study, we demonstrated that CBX increases tumor cell stiffness and significantly reduces lung metastasis. Our study is the first to provide evidence that reducing cell motility by increasing cell stiffness might be effective as a novel anti-metastasis approach in vivo.

Challenges in treatment of patients with non-classic congenital adrenal hyperplasia

Congenital adrenal hyperplasia (CAH) due to 21α-hydroxylase deficiency (21OHD) or 11β-hydroxylase deficiency (11OHD) are congenital conditions with affected adrenal steroidogenesis. Patients with classic 21OHD and 11OHD have a (nearly) complete enzyme deficiency resulting in impaired cortisol synthesis. Elevated precursor steroids are shunted into the unaffected adrenal androgen synthesis pathway leading to elevated adrenal androgen concentrations in these patients. Classic patients are treated with glucocorticoid substitution to compensate for the low cortisol levels and to decrease elevated adrenal androgens levels via negative feedback on the pituitary gland. On the contrary, non-classic CAH (NCCAH) patients have more residual enzymatic activity and do generally not suffer from clinically relevant glucocorticoid deficiency. However, these patients may develop symptoms due to elevated adrenal androgen levels, which are most often less elevated compared to classic patients. Although glucocorticoid treatment can lower adrenal androgen production, the supraphysiological dosages also may have a negative impact on the cardiovascular system and bone health. Therefore, the benefit of glucocorticoid treatment is questionable. An individualized treatment plan is desirable as patients can present with various symptoms or may be asymptomatic. In this review, we discuss the advantages and disadvantages of different treatment options used in patients with NCCAH due to 21OHD and 11OHD.

An "essential herbal medicine"-licorice: A review of phytochemicals and its effects in combination preparations

ETHNOPHARMACOLOGICAL RELEVANCE

Licorice (Gancao in Chinese, GC), the dried root and rhizome of Glycyrrhiza uralensis Fisch., Glycyrrhiza inflata Bat. or Glycyrrhiza glabra L., is an "essential herbal medicine" in traditional Chinese medicine (TCM). There is a classic traditional Chinese medicine theory says that "nine out of ten formulas contain licorice" and licorice is considered as one of the most important herbal medicine which can reduce toxicity and increase efficacy of certain herbal medicine while it is combined application. In addition, it is a "medicine food homology" herbal medicine and also be widely used as a health food product and natural sweetener. However, no systematic literature review has been compiled to reveal its superiority. Herein, the aim of this work is to develop an overview of the state on phytochemicals, as well as effects of licorice in combination preparations, which can provide better understand the superiority of licorice and the special position in the application of TCM. Besides, ethnobotany, ethnopharmacological uses, quality control and toxicology of licorice have also been researched, which would provide reference for future clinical and basic research needs.

MATERIALS AND METHODS

The information about licorice was collected from various sources including classic books about Chinese herbal medicine, and scientific databases including scientific journals, books, and pharmacopoeia. A total of 124 bibliographies, which are published from 1976 to 2019, have been searched and researched.

RESULTS

In this study, the interaction of chemical compounds between licorice and toxic herbal medicine, pharmacological effect of licorice, and the effect of licorice on pharmacokinetics of toxic compounds are considered as the main mechanisms underlying the effects of licorice in combination preparations. Besides, ethnobotany, ethnopharmacological uses and chemical constituents have been summarized.

CONCLUSION

This work comprehensively reviews the state on ethnobotany, ethnopharmacological uses, phytochemicals, combined applications, quality control and toxicology of licorice. It will provide systematic insights into this ancient drug for further development and clinical use.

HMGB1 mediates the development of tendinopathy due to mechanical overloading

Mechanical overloading is a major cause of tendinopathy, but the underlying pathogenesis of tendinopathy is unclear. Here we report that high mobility group box1 (HMGB1) is released to the tendon extracellular matrix and initiates an inflammatory cascade in response to mechanical overloading in a mouse model. Moreover, administration of glycyrrhizin (GL), a naturally occurring triterpene and a specific inhibitor of HMGB1, inhibits the tendon’s inflammatory reactions. Also, while prolonged mechanical overloading in the form of long-term intensive treadmill running induces Achilles tendinopathy in mice, administration of GL completely blocks the tendinopathy development. Additionally, mechanical overloading of tendon cells in vitro induces HMGB1 release to the extracellular milieu, thereby eliciting inflammatory and catabolic responses as marked by increased production of prostaglandin E₂ (PGE₂) and matrix metalloproteinase-3 (MMP-3) in tendon cells. Application of GL abolishes the cellular inflammatory/catabolic responses. Collectively, these findings point to HMGB1 as a key molecule that is responsible for the induction of tendinopathy due to mechanical overloading placed on the tendon.

Deoxycorticosterone-producing adenoma concomitant with aldosterone-producing microadenoma: a challenging combination

OBJECTIVE

To describe the challenging case of a 59-year-old male with a deoxycorticosterone (DOC)-producing adrenal adenoma concomitant with an aldosterone-producing microadenoma.

METHODS

We measured the patient's aldosterone and progesterone levels during adrenal venous sampling (AVS). The steroidogenic enzyme expression was studied with in situ hybridization (ISH). Steroids profiles were determined in the peripheral serum obtained before and after the operation, as well as in the main adrenal tumor.

RESULTS

The patient was diagnosed with primary aldosteronism (PA) based on typical clinical findings. He had an adrenal tumor located at the lower pole of the left adrenal gland. The aldosterone concentration in the adrenal vein proximal to the adrenal tumor was higher than that of the ipsilateral adrenal vein distal to the tumor during the AVS. Progesterone was only elevated in the adrenal vein proximal to the tumor, suggesting that the tumor produced steroids other than aldosterone. The postoperative findings revealed that the main tumor was accompanied by 2 microadenomas. The main adrenal tumor was diagnosed as a DOC-producing adenoma, and one of the microadenomas was diagnosed as aldosterone-producing based on the ISH and the determination of the steroid profiles.

CONCLUSIONS

Concomitant PA masked the key findings of a DOC-producing tumor; the suppression of aldosterone in this patient. Multiple sampling in the adrenal vein considering the location of the adrenal tumor provided a clue to the diagnosis. Progesterone measurement during AVS is easy and may be useful in diagnosing rare adrenal tumors that produce intermediate products in adrenal steroid biosynthesis.

Syndromes that Mimic an Excess of Mineralocorticoids

Pseudohyperaldosteronism is characterized by a clinical picture of hyperaldosteronism with suppression of renin and aldosterone. It can be due to endogenous or exogenous substances that mimic the effector mechanisms of aldosterone, leading not only to alterations of electrolytes and hypertension, but also to an increased inflammatory reaction in several tissues. Enzymatic defects of adrenal steroidogenesis (deficiency of 17α-hydroxylase and 11β-hydroxylase), mutations of mineralocorticoid receptor (MR) and alterations of expression or saturation of 11-hydroxysteroid dehydrogenase type 2 (apparent mineralocorticoid excess syndrome, Cushing's syndrome, excessive intake of licorice, grapefruits or carbenoxolone) are the main causes of pseudohyperaldosteronism. In these cases treatment with dexamethasone and/or MR-blockers is useful not only to normalize blood pressure and electrolytes, but also to prevent the deleterious effects of prolonged over-activation of MR in epithelial and non-epithelial tissues. Genetic alterations of the sodium channel (Liddle's syndrome) or of the sodium-chloride co-transporter (Gordon's syndrome) cause abnormal sodium and water reabsorption in the distal renal tubules and hypertension. Treatment with amiloride and thiazide diuretics can respectively reverse the clinical picture and the renin aldosterone system. Finally, many other more common situations can lead to an acquired pseudohyperaldosteronism, like the expansion of volume due to exaggerated water and/or sodium intake, and the use of drugs, as contraceptives, corticosteroids, β-adrenergic agonists and FANS. In conclusion, syndromes or situations that mimic aldosterone excess are not rare and an accurate personal and pharmacological history is mandatory for a correct diagnosis and avoiding unnecessary tests and mistreatments.

Daily liquorice consumption for two weeks increases augmentation index and central systolic and diastolic blood pressure

BACKGROUND

Liquorice ingestion often elevates blood pressure, but the detailed haemodynamic alterations are unknown. We studied haemodynamic changes induced by liquorice consumption in 20 subjects versus 30 controls with average blood pressures of 120/68 and 116/64 mmHg, respectively.

METHODS

Haemodynamic variables were measured in supine position before and after two weeks of liquorice consumption (daily glycyrrhizin dose 290-370 mg) with tonometric recording of radial blood pressure, pulse wave analysis, and whole-body impedance cardiography. Thirty age-matched healthy subjects maintaining their normal diet were studied as controls.

RESULTS

Two weeks of liquorice ingestion elevated peripheral and central systolic and diastolic blood pressure (by 7/4 and 8/4 mmHg, 95% confidence intervals [CI] 2-11/1-8 and 3-13/1-8, respectively, P<0.05), and increased extracellular volume by 0.5 litres (P<0.05 versus controls). Also augmentation index adjusted to heart rate 75/min (from 7% to 11%, 95% CI for change 0.3-7.5, P<0.05) and aortic pulse pressure (by 4 mmHg, 95% CI 1-7, P<0.05) were elevated indicating increased wave reflection from the periphery. In contrast, peripheral (-3/-0.3 mmHg) and central blood pressure (-2/-0.5 mmHg), aortic pulse pressure (-1 mmHg), and augmentation index adjusted to heart rate 75/min (from 9% to 7%) decreased numerically but not statistically significantly without changes in extracellular volume in the control group. Heart rate, systemic vascular resistance, cardiac output, and pulse wave velocity did not differ between the groups.

CONCLUSIONS

Two weeks of daily liquorice consumption increased extracellular volume, amplified pressure wave reflection from the periphery, and elevated central systolic and diastolic blood pressure.

TRIAL REGISTRATION

EU Clinical Trials Register EudraCT 2006-002065-39 ClinicalTrials.gov NCT01742702.

Functions of connexins and large pore channels on microglial cells: the gates to environment

Microglial cells are not only sensitive indicators for pathology of the central nervous system (CNS), they are a key factor for neurotoxicity and degeneration in many diseases. Neuronal damage leads to reactive gliosis and to activation of microglia including cytoarchitectonic changes accompanied by alterations in surface receptor and channel expression. In this context, the release of neuroactive soluble factors like pro-inflammatory cytokines can result in increased cellular motility and a higher grade of phagocytotic activity. Ligands including glutamate, tumor necrosis factor alpha (TNF-α), cytokines, superoxide radicals and neurotrophins released by microglia have in turn effects on neuronal function and cell death. The current review focuses on large pore and hemichannel function in microglial cells under different conditions of activation and elucidates the role of these channels in cytokine release, as well as putative targets for clinical intervention in case of inflammatory processes. This article is part of a Special Issue entitled Electrical Synapses.

Licorice abuse: time to send a warning message

Licorice extract has always been recognized as a sweetener and a thirst quencher. Its nutritive value is overrated by many who consume significant amounts and are prone to complications. Glycyrrhetic acid, the active metabolite in licorice, inhibits the enzyme 11-ß-hydroxysteroid dehydrogenase enzyme type 2 with a resultant cortisol-induced mineralocorticoid effect and the tendency towards the elevation of sodium and reduction of potassium levels. This aldosterone-like action is the fundamental basis for understanding its health benefits and the wide spectrum of adverse effects. Herein, we present a comprehensive review of licorice along with the reported complications related to excess intake. Despite its apparent use in a few clinical scenarios, the daily consumption of licorice is never justified because its benefits are minor compared to the adverse outcomes of chronic consumption. The review highlights the importance of investigating the dietary habits and herbal remedies which are being used worldwide on cultural and habitual bases rather than reliable scientific evidence. Licorice is a US Food and Drug Administration (FDA) approved food supplement used in many products without precise regulations to prevent toxicity. Increased awareness among the public is required through TV commercials, newspapers, internet sites, magazines and product labels regarding the upper limit of ingestion and health hazards associated with excess intake. We hope that this review will serve as a warning message that should be transmitted from physicians to patients to avoid excessive licorice intake as well as a message to the FDA to start regulating the use of this substance.

Licorice induced hypokalemia, edema, and thrombocytopenia

Licorice originates from the root of Glycyrrhiza glabra, which has a herbal ingredient, glycyrrhizic acid, and has a mineralocorticoid-like effect. Chronic intake of licorice induces a syndrome similar to that found in primary hyperaldosteronism. Excessive intake of licorice may cause a hypermineralocorticoidism-like syndrome characterized by sodium and water retention, hypertension, hypokalemia, metabolic alkalosis, low-renin activity, and hypoaldosteronism. In this case report, an association of hypokalemia, edema, and thrombocytopenia that is developed due to the excessive intake of licorice is presented. There are case reports in the literature, which suggest that toxicity findings may emerge with hyperaldosteronism-like manifestations such as hypokalemia, edema, and hypertension. However, any knowledge of thrombocytopenia as a resultant was not encountered among these reported toxic effects. Our case is important because it shows that the excessive intake of licorice may cause a toxic effect in the form of thrombocytopenia. This report is the first presented case to show thrombocytopenia due to licorice syrup consumption.

Hypertension Secondary to Ingestion of Licorice Root Tea

Objective:

To report a case of hypertension secondary to ingestion of licorice root tea.

Case Summary:

A 46-year-old African American female with newly diagnosed stage 1 hypertension presented with a blood pressure measurement of 144/81 mm Hg and a reduced plasma potassium level of 3.2 mEq/L. The patient attempted lifestyle modifications prior to initiating an antihypertensive agent, but at a follow-up appointment, her blood pressure remained elevated. A current laboratory panel revealed a depressed morning plasma aldosterone concentration (PAC) of 5 ng/dL and low morning plasma renin activity (PRA) of 0.13 ng/mL/h. Later it was revealed that the patient regularly (1–2 cups/day) consumed “Yogi Calming” tea, a blend of herbs, including licorice root. The patient was advised to discontinue consumption of the herbal tea, and at a subsequent appointment, her blood pressure was 128/73 mm Hg and her laboratory panel had improved, including serum potassium concentration of 4.1 mEq/L, PAC of 6 ng/dL, and PRA of 0.19 ng/mL/h.

Discussion:

Excessive consumption of licorice has been well documented to cause pseudohyperaldosteronism, characterized by hypertension, hypokalemia, and suppressed plasma renin and aldosterone levels. Glycyrrhizin, the active ingredient in licorice, inhibits 11β-hydroxysteroid dehydrogenase type 2, an oxidase responsible for the conversion and inactivation of cortisol to cortisone. Chronic ingestion of licorice-containing foods has been demonstrated to cause pseudohyperaldosteronism. These include soft candies, lozenges, and dietary supplements, but licorice-containing teas have been infrequently described. Based on the Naranjo probability score, our patient's hypertension appears to have been a probable licorice-induced reaction secondary to a licorice-containing tea.

Conclusions:

Herbal and dietary supplements are frequently consumed by patients without full knowledge of the contents of the products or the impact on their health. In clinical practice, when hypertension is accompanied by hypokalemia and reduced PRA and PAC, licorice consumption should be investigated and causal hypertension ruled out.

Liquorice health check, Oro-dental implications, and a case report

Liquorice has an active substance, Glycyrrhizin which inhibits the conversion of precursor cortisol to cortisone by inhibiting the enzyme 11-betahydroxysteroid dehydrogenase. When imbibed, liquorice acts like hyperaldosteronism which presents with typical symptoms including high blood pressure, low blood potassium, and muscle pain and weakness. This article appraises physiological and pharmacological effects on health of liquorice, critiques products containing liquorice, describes a typical case report of liquorice-induced hypertension, and appraises oral effects from consumption of liquorice products.

Pseudohyperaldosteronism, liquorice, and hypertension

Consumption of large quantities of liquorice can cause hypokalemia and hypertension. These effects are associated with increased cortisol-mediated activation of renal mineralocorticoid receptors and hypoaldosteronism. The authors describe a patient with long-standing hypokalemia and uncontrolled hypertension related to excessive ingestion of liquorice. The case highlights the importance of obtaining a detailed dietary history, especially considering the increasing use of liquorice-containing foods, teas, and herbal products. The authors also discuss secondary causes of hypertension, focusing on pseudohyperaldosteronism.

Gap-junction blocker carbenoxolone differentially enhances NMDA-induced cell death in hippocampal neurons and astrocytes in co-culture

The beneficial or detrimental role of gap junction communication in the pathophysiology of brain injury is still controversial. We used co-cultures of hippocampal astrocytes and neurons, where we identified homocellular astrocyte-astrocyte and heterocellular astrocyte-neuron coupling by fluorescence recovery after photobleaching, which was decreased by the gap junction blocker carbenoxolone (CBX). In these cultures, we determined the cell type-specific effects of CBX on the excitotoxic damage caused by N-methyl-D-aspartate (NMDA). We determined in both astrocytes and neurons the influence of CBX, alone or together with NMDA challenge, on cytotoxicity using propidium iodide labeling. CBX alone was not cytotoxic, but CBX treatment differentially accelerated the NMDA-induced cell death in both astrocytes and neurons. In addition, we measured mitochondrial potential using rhodamine 123, membrane potential using the oxonol dye bis(1,3-diethylthiobarbituric acid)trimethine oxonol, cytosolic Ca(2+) level using fura-2, and formation of reactive oxygen species (ROS) using dihydroethidium. CBX alone induced neither an intracellular Ca(2+) rise nor a membrane depolarization. However, CBX elicited a mitochondrial depolarization in both astrocytes and neurons and increased the ROS formation in neurons. In contrast, NMDA caused a membrane depolarization in neurons, coinciding with intracellular Ca(2+) rise, but neither mitochondrial depolarization nor ROS production seem to be involved in NMDA-mediated cytotoxicity. Pre-treatment with CBX accelerated the NMDA-induced membrane depolarization and prevented the repolarization of neurons after the NMDA challenge. We hypothesize that these effects are possibly mediated via blockage of gap junctions, and might be involved in the mechanism of CBX-induced acceleration of excitotoxic cell death, whereas the CBX-induced mitochondrial depolarization and ROS formation are not responsible for the increase in cytotoxicity. We conclude that both in astrocytes and neurons gap junctions provide protection against NMDA-induced cytotoxicity.

Carbenoxolone induces oxidative stress in liver mitochondria, which is responsible for transition pore opening

Carbenoxolone (Cbx), a derivative of glycyrrhetinic acid, which has been found to affect mineralocorticoid and glucocorticoid receptors, induces swelling and membrane potential collapse when added to Ca(2+)-loaded liver mitochondria at 10 microM concentrations. These effects are strictly correlated with hydrogen peroxide generation, increase in oxygen uptake, and sulfhydryl and pyridine nucleotide oxidation. Cyclosporin A, bongkrekic acid, and N-ethylmaleimide completely abolish all the above-described effects, suggesting that Cbx can be considered an inducer of mitochondrial permeability transition by means of oxidative stress. Cbx can also trigger the apoptotic pathway because the above events are also correlated with the loss of cytochrome c. These effects are probably related to the conjugated carbonyl oxygen in C-11, which produces reactive oxygen species by interacting with the mitochondrial respiratory chain, mainly at the level of complex I but, most likely, also with complex III. The oxidative stress induced by Cbx, which is responsible for pore opening, excludes that this is related to a genomic effect of the compound.